Methods and systems for non-cooperative automatic security screening in crowded areas

ABSTRACT

The present invention is a multi-threat detection method and system for high-traffic areas, such as airports, other mass-transit hubs, malls, symposiums, and the like. The detection methodology comprises a set of detection blocks, each performing different functions, and taking the information resulting from each block and entering it into one or more detection algorithms. The blocks comprise microwave detectors, co-polarization versus cross-polarization processors, magnetometers, and cameras (optional). The values calculated by the blocks are entered into machine learning algorithms which detect a threat if a threshold value is met. The detection occurs at a distance and the alarm may be silent, such that authorities are able to address threats without the target being aware. The alarm is also able to differentiate among varying threats based on the values calculated. No shadowing problems exist, and thus several targets may be monitored simultaneously without slowing down the speed of processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application claims priority to U.S. ProvisionalPatent Application Ser. No. 62/345,064, filed Jun. 3, 2016; it is also aContinuation in part of U.S. Non-provisional patent application Ser. No.15/596,345, filed May 16, 2017 which is a Continuation in part of U.S.Non-provisional patent application Ser. No. 14/964,328, filed Dec. 9,2015 and is a Continuation-in-part of U.S. Non-provisional patentapplication Ser. No. 14/319,222, filed Jun. 30, 2014, and is aContinuation in part of U.S. Non-provisional patent application Ser. No.14/259,603, filed Apr. 23, 2014 which is currently issued as a U.S. Pat.No. 9,330,549 issued May 3, 2016; and it is also a Continuation in partof U.S. Non-provisional patent application Ser. No. 14/160,895, filedJan. 22, 2014 which is currently issued as a U.S. Pat. No. 9,282,258issued Mar. 8, 2016; and is also a Continuation in part of U.S.Non-provisional patent application Ser. No. 13/528,412, filed Jun. 20,2012 and currently issued as a U.S. Pat. No. 9,304,190 issued Apr. 5,2016; said applications and their disclosures being incorporated hereinby reference in their entireties.

FIELD OF THE INVENTION

This invention is in the field of multiple threat detection systems.Particularly this invention is in the field of detecting concealed orhidden improvised explosive devices (IEDs), metallic weapons and/orshrapnel, and radioactive and nuclear materials.

BACKGROUND ART

The closest threat detection system to present invention is the RapiscanSystems Secure 1000 SP. The Secure 1000 SP uses backscatter technologyas well as image processing software and an operator interface to screenpassengers for a wide range of potential threats including liquids,contraband, ceramics, explosives, narcotics, concealed currency andweapons. The Secure 1000 SP generates a front and back scansimultaneously. The Secure 1000 SP can detect small objects and threatsconcealed on a passenger. It can detect organic and inorganic threats,metals and non-metallic objects and can detect concealed liquids,ceramics, weapons, plastic explosives, narcotics, metals, contraband,currency etc. The Secure 1000 SP requires one pose with no additionalmovement by the passenger, a full scan can be completed in seconds. TheSecure 1000 bounces very low dose of x-rays off of a person to generatean image. This image is then analyzed by an operator to identifyconcealed potential threats.

The Rapiscan Systems Secure 1000 is limited in that it requires a personto be in a single pose for scanning, it requires an operator todetermine what threats are present and to review the scanned images, ituses x-rays for scanning, it only performs backscatter and no passthrough imaging, at it is designed to work at a security checkpoint asopposed to use in an array where it can scan multiple individuals andtheir luggage without causing a security bottleneck. The RapiscanSystems Secure 1000 is incapable of detecting radiation/nuclearmaterials.

There is a need for multi-threat detection systems with very shortprocessing time allowing detection of a variety of threatssimultaneously.

Most of the threat detection technologies that have been used in thesecurity field so far require some cooperation from the inspectedpeople. The degree of expected cooperation varies from relatively mildrequirement to stand in certain position for a certain time to theultimate “take everything out of your pockets” request. Whatever thecooperation requirements are, somebody has to ensure that the inspectedpeople cooperate properly. This means that even for fully automaticsystems, such as metal detectors, the performance will depend on theskills and motivation of the security staff, and the need to have suchstaff near every inspection system makes operational costs very high.

A direct consequence of the standard cooperative inspection approach isprohibitive cost of using existing inspection systems in crowded places:even for automatic detection systems, too much personnel would be neededto ensure that everybody cooperates properly.

The only widely used non-cooperative security-related hardware are CCTVcameras, which often work without people even knowing that they areviewed. However, CCTV cameras typically require human operators tointerpret video stream, and are thus only useful after the incident hasalready happened. One of the main problems currently facing the securitycommunity is the growing dissatisfaction of the public and businesseswith the high operational costs and disruptions of normal functioning ofthe protected sites that are often associated with current securitymeasures. This dissatisfaction, which is for the most part totallyjustified, not only threatens to undermine the current achievements inthe traditional security areas, such as aviation security, but alsoprevents deployment of security solutions to other high-risk locations,such as urban transport infrastructure (metro, trains, buses), masssports and political events, government buildings etc.

Dramatic reduction of the operational costs and the inconveniencescaused by security measures to the protected sites would thus be the keyto maintaining and increasing both the level and proliferation ofsecurity measures.

SUMMARY OF THE INVENTION

The present invention uses microwave detection to find non-metallicobjects that are hidden, it uses cross-polarized microwaves and passivemagnetometry to detect hidden metallic weapons or shrapnel, and usesgamma ray detection to find radioactive materials. Each of thesetechnologies provide threat detection, combined these technologies canprovide detection of even more types of threats.

The present invention using microwave detection used in conjunction withcross-polarized microwave detection detects IEDs with shrapnel. Whenusing microwave detection, reflective or pass through, dirty bombs aredetectable. And the combination of cross polarized microwave detectionwith gamma detection allows for detection of radioactive/nuclearmaterial that is shielded by metal.

The present invention allows for real time scanning of individuals,multiple individuals at once, for reflected microwave, cross polarizedmicrowave, and radioactive/nuclear scanning either in a securitycheckpoint or in an open array/portal that people walk through. Thedevices in an array/portal can be disguised as advertisement space,information boards, etc. The present invention can be used inconjunction with facial recognition software to track a suspiciousindividual through a given space. The present invention can be use witha limited access entry portal that can isolate an individual to performsubsequent scans in order to determine, automatically, if a threat isdetected or if there is a false alarm all while minimally disruptingthroughput of the entry portal. The present invention can also beintegrated into a system of multiple scan points and use subjecttracking in order to perform additional scans and automaticallydetermine threat presence. Furthermore, the invention can be practicedin an automatic manner or be reviewed by operators. The invention canalso be used to perform pass through and radiation/nuclear scans ofrolling luggage, handbags, briefcases, backpacks, etc. The presentinvention also performs automatic facial recognition from a distance,against a database of known or suspected terrorists and provide analert. The present invention provides different alerts based upon thetypes of materials found.

An appreciation of other aims and objectives of the present inventionand a more complete and comprehensive understanding of this inventionmay be achieved by referring to the drawings, and by studying thedescription of preferred and alternative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be discussed in further detail below withreference to the accompanying figures in which:

FIG. 1 provides a schematic block diagram of a multi-threat detectionsystem.

FIG. 2 shows a detailed schematic of a threat detection block comprisingan active microwave detection system.

FIG. 3 shows the microwave path and reflection off a target's coat andbody boundaries (first and second boundaries, respectively).

FIG. 4 further details a microwave (MW) beam's reflection in (a) theabsence, and (b), (c), (d) the presence of hidden dangerous objects.FIG. 4(b) shows an example of the location of explosives on the humanbody under the coat or other garment. FIGS. 4(c) and 4(d) show theoptical paths and distances measured or calculated by the claimedinvention in the case of hidden objects.

FIG. 5 shows detectors in the cross-polarization method of the presentinvention.

FIG. 6 is a schematic image of a real hidden metal threat (gun) and thedetection of said hidden metal threat obtained via thecross-polarization method of the present invention.

FIG. 7 is a schematic block diagram of the nuclear material detectionblock.

FIG. 8 shows a spectrum of cesium-137 obtained by sodium iodide (NaI)detector (prior art).

FIG. 9 shows a graphical example of transmitters with a wide-angleradiation pattern 91 in polar coordinates, at a frequency of 11 GHz. Themain lobe is 90.7 degrees at 3 dB beamwidth 92.

FIG. 10 shows a graphical example of receivers with a wide-angleradiation pattern 101 in polar coordinates, at a frequency of 10 GHz.The main lobe is 90 degrees at 3 dB beamwidth 102.

FIG. 11 shows an example illustration of a wide angle of inspectiongreater than 90 degrees of an inspected area (transmitters and receiversare located on each of the left and right pillars).

FIG. 12 shows an example illustration of a wide zone of inspection andoperating pillars as a single system and as a complex system. A singlesystem according to the present invention comprises means fortransmitting and receiving wherein both means are located on one pillaror block. A complex system according to the present invention comprisemeans for transmitting and receiving wherein the transmitting means andreceiving means are located on two or more separate pillars which mayfurther correspond with each other.

FIG. 13 shows an example flowchart illustration of the real-timeprocessing (greater than 15 frames per second) of signals received andthe fast switching, according to the present invention. In FIG. 13, eachbold line represents different levels of processing as related to thefast switching. The total time estimated for each specific switching isexemplified in the figure; for example, the lowest bold line representsa process of switching between individual transmitting antennas in anarray of transmitters and the time required, according to the presentinvention, for information (statistic/data) collection by an individualtransmitter (occurring in the order of 10⁻⁷ seconds). Summing alltransmitter (Tx) switching, and combining all frequencies into oneframe, the result in this particular example is at least 15 frames persecond.

FIGS. 14A-14B. FIG. 14A shows a graph of cross-polarized vs.co-polarized amplitudes for (1, square points) a body without objects,(2, circular points) metals on a body (shrapnel and a gun), and (3,triangular points)) a dielectric on a body (wax). FIG. 14B shows a graphrepresenting discrimination between a body without objects 41, a bodywith metals 42, and a body with dielectrics 43, obtained by employing anSVN algorithm with Principal Component Analysis (PCA) datapre-processing. FIG. 14A represents experimental data collected inCross- and Co-polarized amplitudes. FIG. 14B represents the same data asin FIG. 14A but after pre-processing in the PCA algorithm, and incoordinates of the two main principal components 1 and 2. The PCAprocessing removes the influence of measurement units in raw data andcan also removes noise components from raw data (e.g., when more than 2“row” parameters are used). FIG. 14B represents, in particular regions,how to differentiate data for three different cases (even if some ofpoints are very close to one another): body without objects 41, a bodywith metals 42, and a body with dielectrics 43. The Principal ComponentAnalysis (PCA) algorithm used for pre-processing, as exemplified in FIG.14B allows for differentiation of, e.g., row data which partly overlap,as exemplified in FIG. 14A. After the PCA processing, an appropriateclassification algorithm can be used, such as, e.g., support vectormachines or one of the following: Bayes classifier, neural networks,gradient boosted trees, K-nearest values, etc.

FIG. 15 shows a total magnetic strength effect in nT (nano Tesla) from atarget/person moving/running with pneumatic rifle (with 40 cmferromagnetic barrel) attached at one of the target's shoulders invertical direction relative to the ground. The total magnetic strengtheffect means modulus of vector calculated from three axis' ofmagnetometer values in X, Y and Z directions. Each experiment (see FIGS.15-21) runs for approximately 45 seconds, when the person had 3 runs(direct and back) at each at varying distances (middle of portal—120 cmapprox. from both magnetometers (see two peaks at time interval 1-17 secin X axis of FIG. 15, left—60 cm approx. from magnetometer #1 (sensor #1on FIG. 15), and 180 cm from magnetometer #2 (sensor #2 on FIG. 15). seetwo peaks at time interval from 17-29 sec in X axis of FIG. 15, right—60cm approx. from magnetometer #2 and 180 cm from magnetometer #1, see twopeaks at time interval 29-41 sec in X axis of FIG. 15, within the portalcreated by the two magnetometers. The strength of the peaks aredifferent depending on direct vs. back running, since the ferro object(as a rule) was attached at one of person side, meaning that the ferroobjects are closer or further, respectively, from the magnetometer evenif the person is moving/running along the same line of the portal.

FIG. 16 shows total magnetic strength effect in nT (nano Tesla) from aperson/target moving without any ferro-magnetic metal. The path and timeof the person running is the same as described at FIG. 15.

FIG. 17 shows total magnetic strength effect in nT (nano Tesla) from aperson/target moving with a pneumatic gun (with a 10 cm ferromagneticbarrel) attached at one of the target's sides in a vertical directionrelative to the ground. The path and time of the person moving is thesame as described at FIG. 15.

FIG. 18 shows total magnetic strength effect in nT (nano Tesla) from aperson/target moving with a laptop in a rucksack. The path and time ofthe person moving/running is the same as described at FIG. 15.

FIG. 19 shows total magnetic strength effect in nT (nano Tesla) from aperson/target moving with a phone, keys and coins in the target'spockets. The path and time of the person moving/running is the same asdescribed at FIG. 15.

FIG. 20 shows total magnetic strength effect in nT (nano Tesla) from aperson/target moving/running with a pneumatic rifle (with a 40 cmferromagnetic barrel) attached at one of his shoulders in a verticaldirection relative to the ground, with a noise effect (100 to 500 nT)(magnetometers were mounted into the portal at 1 meter above the floor)produced from the server computer and the microwave portal at switch“ON” regime.

FIG. 21 shows the same effect as that in FIG. 20. but from aperson/target moving/running with a pneumatic rifle with the noise cutoff via frequency filtering (a useful effect is below 5-10 Hz).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, for purposes of explanation, specificexamples are set forth to provide a thorough understanding of thepresent invention. However, it will be apparent to one skilled in theart that these specific details are not required in order to practicethe present invention. The same techniques can easily be applied toother types similar systems.

The present invention is the first system/method capable ofnon-cooperative automatic security screening in crowded areas. It isoperator-free and only notifies the security personnel about actualfound threats without the need for constant monitoring/video or otherdata streams. This would lead to, among other benefits, a dramaticreduction of operational costs.

The present invention has been demonstrated to detect both metals(weapons), dielectrics (explosives), and mixed threats (e.g., improvisedexplosive devices, IEDs, with shrapnel) in real time and from a standoff distance, coupled with very low false alarm rates. Being anon-cooperative inspection system, the present invention causes verylittle inconvenience to the general public and, unlike prior art methodsand systems, it causes no disturbance to the normal operation of aprotected site.

As radio waves travel through the air, they travel in a way similar towaves of water moving across the surface of the ocean. The shape of asimple radio signal can be depicted as a repeated up and down movementor vibration. This up and down motion of the wave takes place in threedimensions. A wave which is polarized parallel to the plane ofpropagation is called a horizontally polarized wave. A wave which ispolarized perpendicular to the plane of propagation is called avertically polarized wave. The height or intensity of the wave is calledthe amplitude of the wave. The idea of polarization is applicable to allforms of transverse electromagnetic waves, whether they are radio wavesat microwave frequencies, or light waves such as those emitted by aflashlight.

The power levels radiated by the present invention are much lower thanconventional radar systems or than those generated by x-ray or otherimaging systems that are currently employed to detect objects at theentry of an airport or a courtroom. In general, some of the preferredembodiments of the invention operate in the MHz or GHz frequency bands.Different radio or microwave frequencies offer different benefits anddisadvantages for the object detection provided by the presentinvention. Although the description of some embodiments of the inventioninclude specific references to particular frequency ranges, the systemmay be beneficially implemented using a wide variety of electromagneticradiation bands.

Any threat detection system that would not require cooperation from theinspected people should meet the following minimal list of requirements:

(1) It should not require inspected people to alter their normalbehavior in a significant way. At most, mild crowd control measures suchas queue fences may be used. Ideally, the person would not even knowabout the fact of inspection.

(2) It should not require constant attention from security personnel,who would only occasionally receive information about an alarm vianetwork (possibly, wireless), and may be busy with other things rest ofthe time.

(3) It must be followed by an established procedure to resolve alarms,e.g. diverting people who caused alarms for additional inspection,automatically controlling some access blocking system, using facerecognition or other analytic software, etc.

(4) It should have very low false alarm rate, so that it would not causeinconvenience to the security personnel, the public, or the protectedsite.

(5) It should have high throughput and work unattended in anoperator-free mode, so that no queues are created in the place ofinspection.

If these requirements are met, the system would not interfere with thenormal operations of the protected site, and operational costs would bevery low due to savings on personnel.

The present invention is based on sending very low-power centimeterradio waves into a wide-angle area, and receiving and analyzingscattered and transmitted waves. Different types of materials producedistinctively different responses to radio waves. It has also been foundthat the human body is a good reflector for radio waves in the usedfrequency range, so it looks like a large reflective surface; thatdielectrics are partially transparent for radio waves and have arefractive index larger than 1, which leads to the apparent increase ofthe flight path traveled by the wave between the emitter and thereceiver; and that the edges of metallic objects lead to a rotation ofthe polarization of the incident wave.

The principles behind the present invention have are described herein.The systems of the present invention comprise a flexible system that canbe implemented in a portal configuration, as a longer-range flat-panelconfiguration, or as a combination of the two. The present inventionoperates in two distinct modes: “reflection” and “transmission.”

In the stand-off (i.e. far range) “reflection” mode, the system measuresthe radio waves reflected from objects in different polarizations. Theposition of scatterers with different reflecting properties on the sceneare then reconstructed from the measured complex electromagnetic fieldusing high-speed parallel processing units. The obtained distribution ofscatterers may then be compared to an optical or depth image of thescene. Properties of found dielectrics, such as thickness, shape, andpermittivity, can be obtained from subsequent automatic analysis andused in the decision-making procedure to distinguish between dangerousand benign objects. Analysis of the response of the scene in differentpolarizations allows for detection of metallic objects.

In the close-range “transmission” mode the system measures the timeshift and amplitude of electromagnetic waves passing right through thedielectric when the person is between the emitting and receivingantennae. Any apparent increase of the flight path signals a potentialpresence of a substance with a refractive index larger than 1, ascalculated between the antennae. Further analysis involving, e.g.,building multiple tomographic images at different time slices allows anoperator to detect the presence of dielectric objects on a human body,in backpacks, or in wheeled luggage.

The present invention collects data at a rate of tens of frames persecond and then analyzes them using high-speed parallel processingunits, thus achieving true real time differentiation and performance.

The system may be complemented by additional video or depth sensors, sothat a photograph of a suspect carrying a threat as well as superimposedinformation about the threat location and threat type may also be sentthrough an existing security network. Alternatively, the presentinvention has its own user interface, which runs on a remote device andcan accumulate information from several systems. There is no need forany staff member or employee to constantly monitor the data from thesystem: in a preferred embodiment, the system only sends informationwhen a threat has been detected.

The present invention fulfills the following requirements for a systemcapable of non-cooperative operation in crowded environments withoutdisrupting normal operation of the site: (1) it is fully automatic andoperator-free; (2) it works in real time from standoff distance ofseveral meters; (3) it inspects multiple people simultaneously; (4) itcan detect a wide range of threats, including improvised ones; (5) ithas very low false alarm rate.

Detection of Metallic Weapons and Shrapnel. Metallic threats aredetected by automatically comparing relative intensities of signalsreflected from some point with different polarizations. The radio wavesemitted towards the scene are polarized along one or several directions.Reflected waves are measured both in the same and in the orthogonalpolarization to the incident one. Metallic objects having a complexshape, such as guns, tend to rotate the polarization of the incidentwave by 90 degrees. Distributions of the reflecting points across thescene measured in two orthogonal polarizations are automaticallycompared, and regions with excess cross-polarized component are markedas potential metallic anomalies. Parameters and trajectories of theseanomalies are then automatically tracked within many consecutive frames,and compared with the location of dielectric objects found by therespective algorithms. Then the decision is made whether the anomaly isthe actual metallic object, an artifact, or part of a mixed(metal-dielectric) threat. This decision is made once an anomaly isdetected. Whether that anomaly is a metallic object or an artifact isbased on the number of total anomalies found on the same target duringthat target's presence in the inspection area. A mixed metal-dielectricthreat may also be determined by comparing locations of total anomaliesversus dielectric anomalies. The objects considered dangerous arereported to the user in the form of a photograph with superimposedrectangle showing the location of the threat.

Metal detection capability is currently implemented in the walk-throughportal configuration of the present invention. Another way the presentinvention can detect large metallic objects hidden in luggage (e.g., ofthe type used in Boston Marathon attack on Apr. 15, 2013) is bydetecting anomalous blocking of the radio waves passing through thebackpack (“transmission”) in conjunction with detection of theproperties of reflected waves (“reflection”). This allows the system todetect large metallic objects in backpacks even if those objects do nothave the characteristics that cause a strong cross-polarization effect.

Detection of Suicide Belts. Dielectrics are detected by automaticallyanalyzing the areas with an apparent increase of the flight path of thewave on its way from emitter/transmitter to receiver. Depending on theconfiguration of the system and location of the moving person, thisincrease appears either on the reconstructed reflected field(“reflection” mode) or on the field transmitted through the dielectric(“transmission” mode). The capability to detect dielectrics has beendemonstrated during testing at an industrial facility. The rate of falsealarms was shown to be less than 1%, while the detection rate forrealistic explosives and/or simulants of the same, used was about 90%.Additionally, even if the explosive charge is completely surrounded byshrapnel, it can still be detected by the characteristic signature ofmetals (see above regarding detection of metallic weapons and shrapnel).

Detection of bombs in luggage. The present invention may also look forthreats not only on a human body but also in wheeled or carried luggage.The main difference between detecting explosives on a person versus inluggage is that a typical luggage item may contain large amounts ofdielectric elements (e.g. clothes, shoes, paper, plastic), which shouldnot be mistaken for an explosive substance. One can rely here on thefact that most explosives are somewhat denser than widespread benigndielectric materials. The typical density of a standard explosive isabout 1.7 g/cm³, while the density of clothes, shoes, dry paper, etc. isusually significantly lower. Thus, an explosive hidden among otherdielectrics in a suitcase would appear to the system as a dielectricanomaly consisting of a dense, core surrounded by a less densedielectric peel with both the core and the peel increasing the apparentpath of the wave but to different degrees. The present invention uses apath-based “peeling” algorithm to separate the dense core of the anomalyfrom surrounding materials. Then the parameters such as apparentincrease of the wave path, amplitude of the corresponding peak, volumeof the anomaly, etc. are determined separately for the core and for thepeel.

Example of distributions of a path increase and the corresponding peakamplitudes for anomaly cores and peels are provided in the Drawings(see, e.g., FIGS. 14A and 14B). Each point represents a dielectricanomaly found on a person passing through the system with a largebackpack, wherein the backpack may or may not contain an explosivesimulant (indicated via squares, benign, and indicated via circles,simulant), or with different simulants hidden within suicide belts(indicated via diamonds).

These and other similar graphs are used to train an automatic dataanalysis system, which is then capable of automatic detection of denseobjects with required characteristics surrounded by less dense elementsin luggage. The automatic data analysis system is based on machinelearning algorithms. While on every individual plot, the regionscorresponding to luggage with and without threats may largely overlap,multidimensional machine learning algorithms can separate them veryreliably. For example, two machine learning algorithm may be used: (1)Mahalanobis distances—a simple algorithm, in which the decision is basedon the distances between the given data point and centers of clusterscorresponding to different decision outcomes (metal, benign) measuredwith standard deviation of/from these clusters. The algorithm is chosenfor its simplicity. (2) Support Vectors Machines (SVM)—kernel basedalgorithm, in which the decision is guaranteed to have the minimal riskof an error. This algorithm is chosen for its versatility. The finaldecision that the object is a particular threat is made if any of thetwo algorithms described above arrives at this decision (i.e., using ORlogic).

Examples of images used and produced by the present invention includebut are not limited to: small backpack containing a large simulant;large backpack with a simulant surrounded by clothes; suitcase withsimulant and clothes carried away from the camera; suitcase withsimulant and clothes carried towards the camera. The coloring/filling ofthe square indicates whether the detected threat is visible by thecamera (filled rectangle), or part or all of it may be obstructed by thebody (unfilled rectangle). For example, an open square may indicate thatthe threat is in a large backpack on the person's back. Thus, thesecurity staff is able to receive a better indication about the type andlocation of the threat even if only one camera is used.

Block 1—3D Microwave Imaging

Block 1 makes it possible to remotely determine the dielectricpermittivity of a moving, irregularly-shaped dielectric object. Thedielectric permittivity of a dielectric object is determined when theobject is placed against the background of a reflector. The methodincludes recording a 3D microwave and a 3D optical range images of aninterrogated scene at the same time moment, digitizing all images andoverlapping them in one common coordinate system; determining a spacebetween the microwave and optical image (as described below),calculating a dielectric permittivity ∈ of the space; and concluding theabsence of hidden dielectric object where the dielectric permittivity isless than a threshold value. If the dielectric permittivity is in thefixed range (for example 2.9-3.1), then the conclusion is made on thepresence of a hidden object.

The detection operates by sending microwaves (in centimeter range)towards a moving target (e.g., a person), and detecting the reflectedwaves afterwards. The data analysis is carried out in real time byhigh-speed GPUs to obtain the image of a potentially hidden object andreceive information about its volume and dielectric properties, whichallows distinguishing between a common object and a potential explosive.This information is then used to automatically assign a threat level tothe found ‘anomaly’ without an operator's involvement.

A system for unveiling a dielectric object in an interrogated space isdisclosed, wherein the interrogated space is located between an innerlayer and an outer layer, comprising at least two microwave (MW) sourcesand at least one MW receiver forming 3D MW images of the interrogatedspace, wherein said 3D microwave images are formed by emitting MWsignals from the MW sources towards the interrogated space, wherein eachMW signal partially reflects off the outer layer (first boundary in FIG.3) and the remainder of the MW signals travels through the intermediaryspace, where the reminder of the MW signals partially reflects off theinner layer (second boundary in FIG. 3), where said MW receiver receivesreflected signals from said outer and inner layer, further comprising acomputer/calculator which is adapted for determining at least twodistances P1 and P2, between at least two sets of points, whereP1=(A2−A1) and P2=(B2−B1); wherein A1 is a point of a first MW beamreflected from the outer layer, and A2 is a point of the same first MWbeam reflected from the inner layer, wherein B1 is the point of a secondMW beam reflected from the outer layer, and B2 is a point of the samesecond MW beam reflected from the inner layer (FIGS. 4 a and c), whereinthe at least two sets of two points are spaced from each other by apredetermined value S; and which is further adapted for calculating thedifference D between P1 and P2 and comparing the difference D with apredetermined threshold value T; and further comprising an alarm adaptedfor indicating a likelihood of a hidden dielectric object between theinner and the outer layer, if the difference between P1 and P2 isgreater than a threshold value T.

Also, a method for unveiling hidden objects in an intermediary space isdisclosed, wherein the intermediary space is located between an innerlayer and an outer layer, comprising sending microwave (MW) signals fromMW sources towards the interrogated space, the signals being partiallyreflected on the outer layer and partially on the inner layer, receivingat a MW receiver a first and a second response of MW signals reflectedback from the outer and the inner layer; the first and the secondresponse signals corresponding to a first and a second 3D MW image,wherein the first 3D MW image corresponds to the outer layer of theinterrogated space, and the second 3D MW image corresponds to the innerlayer of the interrogated space, determining at least two distances, P1and P2, where P1=(A2−A1) and P2=(B2−B1); where A1 is a point of a firstMW beam reflecting from the outer layer and A2 is a point of the samefirst MW beam reflecting from the inner layer, where B1 is the point ofa second MW beam reflecting from the outer layer and B2 is a point ofthe same second MW beam reflecting from the inner layer; wherein A1 andB1 are spaced from each other by a predetermined value S; calculatingthe difference D between P1 and P2, comparing the difference D with apredetermined threshold value T; indicating if the difference D isgreater than the threshold value T. In one embodiment, the methodfurther comprises determining at least a third and a fourth distance P3and P4 from a third and a fourth response signal, where P3=(C2−C1) andP4=(D2−D1), where C1 is the point of a third MW beam reflecting from theouter layer and C2 is a point of the same third beam reflecting from theinner layer, where D1 is a point of the fourth MW beam reflecting fromthe outer layer, and D2 is a point of the same fourth MW beam reflectingfrom the inner layer. P3 and P4 can be used to increase reliability ofan alarm triggered when the difference D between P1 and P2 is greaterthan the threshold value T. P3 and P4 can be determined in essentiallythe same area where P1 and P2 are determined, but using differentviewing angels. P3 and P4 can also be used to detect further hiddenobjects in a different area than where P1 and P2 are determined.

The interrogated space can be between the body of a person and theclothing of this person or between two layers of clothing of a person.The outer layer is preferably formed by the boundary between air and theouter clothing of a person.

3D Microwave Imaging Techniques. Determining the presence of apotentially hazardous object carried by a target 11 is done in thefollowing manner (FIG. 3). Some of the primary emitted MW radiation 12is partially reflected by the first (outer) boundary (usually theperson's coat/jacket/outer garment) forming a reflected beam 13 (seeFIG. 4(a)—an enlarged view of area N—for greater detail). The sameradiation/wave then travels through the coat until reflected by thesecond (inner) boundary, the human body, forming a second reflected beam14. Thus, at least two reflections of the same wave occur—one reflectionoccurs at the outer boundary of the target and/or object (i.e. the firstborder, or air/intermediary space border) and another reflection occursafter the wave travels through the intermediary space and reflects offthe target's body (i.e. the opposite side of the hidden dielectricobject, if present). The measured distance P1 of the intermediary spacebetween the first and second boundaries is recorded and used to detectthe presence of hidden objects, P1=(A2−A1) is the distance between thepoint A2 on the second boundary and corresponding point A1 on the firstboundary. This process is repeated for measuring of at least one otherdistance or continuously for measuring of other distances, allowingmicrowave beams to hit and reflect off of various locations along thefirst and second boundaries. Each additional microwave beam thatreflects off additional locations along the first and second boundariesB1, C1, D1, . . . and B2, C2, D2, . . . allows for measurement ofadditional distances P2, P3, P4, . . . between first and secondboundaries. With microwave signals being emitted and receivedcontinuously, 3D microwave images of the inspected area are created. Thefirst 3D MW image corresponds to the first boundary, and the second 3DMW image corresponds to the second boundary. The method allowsdetermining the presence of hidden dielectric objects on the human bodyunder the outer garment or carried by the person. Area N is enlarged andshown in greater detail in FIG. 4(a). FIG. 4(a) represents a situationwithout a hidden object. FIG. 4(b) illustrates how an explosive might beworn on the body under a coat. In a preferred embodiment of the presentinvention, the hidden objects are explosive materials of componentsthereof. In one embodiment the method of the present invention is usedto unveil hidden suicide bombs in a crowd of moving people. Thedielectric constant of explosives is about three or larger. The MWradiation traveling through a medium with such a high dielectricconstant is equivalent to traveling a longer distance in air and thusthe microwave image of a hidden object is portrayed as a cavityprotruding into the body, as illustrated by FIG. 4(c). This seeminglylonger distance corresponds to a sharp change of the microwave beam pathlength, which is detected by the receivers because the MW beam in afirst area 15 contains extra path gain compared to the MW beam in asecond area 16. By measuring the phase and amplitude of incomingreflected microwaves, the microwave path (i.e. the path of the microwavebeam/signal) can be determined and the sudden sharp change of the pathin certain areas, if present, is registered. Because a microwave travelsmore slowly in an object with a higher dielectric (permittivity)constant, a second border signal takes longer to arrive in the presenceor area of an object (compared to areas where no object is present,e.g., just above, below, or to either side of an object.). If the changein path value exceeds a preset threshold value, it serves as anindication that a hidden object is present.

In the preferred embodiment, the threshold value T is system resolutionin depth in the direction perpendicular to the first and the secondboundaries (i.e. the outer and inner layers, also called borders). Inthe preferred embodiment the resolution is equal to 1 cm. The resolutiondepends on the bandwidth of the MW frequencies used. The resolution isequal to the speed of light in vacuum divided by the doubled bandwidthof the MW frequencies used. Bandwidth of the MW frequencies is typical15 GHz, which thus means 1 cm resolution in depth.

The additional path, h (see FIG. 4(d)), is equal to h=l(( )), where l isthe thickness of the intermediary space, which equals the distance fromthe first boundary to the second boundary including the cavity, ifpresent, as shown by the first area 15 (see FIG. 4(c)), and ∈ is thedielectric (permittivity) constant of the intermediate space. Theadditional path, h, is calculated by subtracting the measured value ofthe second area 16 from the measured value of the first area 15. 15. 15.15. 15.

The first and the second border signals can be used to reconstruct two3D MW images of a person, one corresponding to the outer garment and theother corresponding to the human body, as described above. However, thesignal received from the first border of an interrogated space, due toits small value, may be disrupted by the side lobes (i.e. secondarymaximums) of the signal from the second border. Preferably, asynchronized video image border can additionally be used, if thesignal/noise ratio is low (see FIG. 2).

MW radiation can be emitted from various different angles and thereflected radiation, also travelling from various different angles, issimilarly processed, allowing for accumulation of additional data toimprove the accuracy and resolution of the image and detection process.Various configurations of setups are possible.

Block 2—Co-Polarization Vs. Cross-Polarization Processing.

The purpose of Block 2 is to detect hidden metal weapon and metallicshrapnel. When the present invention is used to detect an object like ahandgun, the detection is more easily accomplished when the handgun isoriented in a way that presents a relatively larger radar cross sectionto the detector. For example, a gun that is tucked behind a person'sbelt buckle so that the side of the gun is flat against the waistpresents a larger radar cross section than a weapon holstered on the hipwith the gun barrel pointing toward the ground and the grip pointingforward or back. In general, the present invention relies on thephysical phenomenon of reflection in which an incident beam ofhorizontal polarization will be partially reflected back as verticalpolarization. The percentage of energy converted to verticalpolarization depends on the shape of the weapon in the plane normal tothe direction of incidence and sharpness (contrary to flat parts) ofdifferent parts of weapon (or shrapnel). If the weapon has a crosssectional shape that has both vertical and horizontal components, then avertically polarized component will be realized even though the objectis irradiated by horizontal polarization.

Measuring the phase of the polarized waves reflected from a person whomay be carrying a concealed weapon is important because the polarizedwaves reflected from a concealed weapon and the polarized wavesreflected from a human body behave quite differently. In general, thereflections from a concealed weapon, while not constant, vary within arelatively confined range. In contrast, the reflections from a humanbody are chaotic. A preferred embodiment of the invention exploits thisgeneralized phenomena by using signal processing methods to distinguishthe relatively well-behaved signals from a concealed weapon from thegenerally unpredictable signals from a human body.

The present invention incorporates the apparatus depicted in FIG. 2 tomeasure amplitude and phase of the returned cross-pole signal. Microwavereceivers 8A and 8B include two detectors each as shown in FIG. 5.Detectors 31 and 32 register received microwave radiation with verticalpolarization and detectors 32 and 34—with horizontal polarization. Inone embodiment this is achieved by placing corresponding polarizationfilters in front of the receivers. Data from the detectors 31-34 entersprocessing component 35, which is a part of the processing unit 5.

The present invention reconstructs a 3D MW image and compares amplitudesof reflected co- and cross-polarization waves in many places/zones ofthe human body simultaneously and in real time. This allows fordetection of concealed weapons, shrapnel, or other items withoutcomparison to pre-stored reference data. In an alternative embodiment ofthe invention the present invention takes reading of multipleindividuals and automatically determines the presence of hidden weapons,shrapnel, or other items simultaneously.

The cross-polarization method partially uses the same equipment(microwave detectors, processing unit, computer, alarm system) aspreviously described 3D microwave imaging (Block 1) for detection ofhidden plastic explosives.

Expected performance of system with co-polarization andcross-polarization technologies. Threat objects detected by suchtechniques include automatic weapons and metallic shrapnel. The area ofdetection includes mainly the chest/front area of a subject body. Thestand-off detection distance threshold is 3-4 meters for automaticweapons. The threat localization is to within 0.2 meters. The shieldingproblem in a crowd (e.g., shadowing of one body behind another is anissue for this type of detection technology).

Block 3—Passive Magnetometry

Due in part to the desire of end users to add more reliable automaticweapon detection capabilities to the present invention, an additionalblock comprising passive magnetometry technology is further included.While co/cross polarization technology, as described above in referenceto Block 2, is expected to perform some sort of automatic weaponsdetection and metallic shrapnel on the surface of IED (improvisedexplosive device), that technology has numerous limitations, includingbut not limited to the following: (1) the front area of a subject body(i.e., mainly the chest area) is considered; (2) shadowing is a problem(i.e., one subject body being blocked by another subject body or more);(3) FAR (false alarm rate) to other body parts/areas (e.g., gender andshoulder areas); (4) low performance to flat metallic surfaces (e.g., aweapon attached/placed against a subject body, at a near zero angle);and (5) FAR to benign metal goods with sharp edges.

Passive magnetometry techniques, as described hereinbelow, solve thelimitations noted above with regard to cross/co-polarization technologyand may be added as low cost solutions to the limitations of currentstate of the art security systems and methods.

Magnetometers may be coupled with co- and cross-polarization techniques,as described above, in order to further assist in differentiationamongst types of automatic weapons as well as the general type of metalthreat. Magnetometer have several advantages over conventional metaldetectors, including but not limited to: (1) higher in safety, due tothe fact that magnetometers do not emit anything; (2) no screeningpreparation necessary (e.g., no removal of jewelry, phone, wallet,etc.); (3) throughput speed is 4-5 times faster than conventional metaldetectors (magnetometer screening devices can screen about 1000 targetsor more per hour); (4) no calibration necessary (due to the earth'smagnetic field being everywhere, there is no need to calibrate and makesmagnetometers very portable); and (5) no secondary screening necessary(e.g., no need for a full body cavity search in any situation).

Examples of particular magnetometers which may be used are as follows:(1) Bartington (single axis fluxgate Mag670 or three-axis fluxgateMag690); (2) Metrasense, Cellsense Plus (it is noted with regard to thistype of magnetometer, that this type also detects knives, tattoo guns,lighters, and firearms; it is also noted that with regard to this typeof magnetometer, that two Cellsense units may be positioned in paralleland at a distance to create a portal operation, the portal being up to2.5 meters in width, in order to provide detection of ferromagneticmetal from distance above 1 meter).

Experiments performed show that most weapons are visible using themagnetometer technique within 2 meters or less from a magnetometersensor. Larger weapons result in greater significant changes; however,more modern (i.e. smaller or using less metal) weapons result in asmaller signature at distances greater than 2 meters. One suchexperiment is described in detail below:

Magnetometer experimental results. Two Three-Axis Fluxgate Magnetometers(Bartington, Mag690) are connected to SPECTRAMAG-6 Data AcquisitionModule via a 5 meter cable. The SPECTRAMAG-6 is connected to a processor(e.g., computer, PC) for digital data collection from the magnetometers.The entire setup is also coupled to the cross- and co-polarizationtechnology of the present invention, such that the two technologies workin parallel. The two magnetometers are positioned at 2.4 meters awayfrom each other to create a portal, on the portal's frame comprising co-and cross-polarization technology, at 100 cm from the floor. Objectstested included the following threat objects and its imitators:pneumatic rifle, pneumatic gun, ferro barrels (10, 40 cm long), fireextinguisher (1 liter, 4 liters), and vax with nuts. Objects testedincluded the following benign metal objects: notebook (in rucksack),mobile phones, keys/money, zipper/belts, drill (in rucksack). Tests wereperformed comprising 1 person, 2 persons, and 3 persons simultaneouslyinside the inspection area of the portal, each at varying distances(e.g., middle—120 cm approx. from both magnetometers, left—60 cm approx.from magnetometer #1 (sensor #1 on FIG. 15 for example) and 180 cm frommagnetometer #2 (sensor #2 on FIG. 15 for example), right—60 cm approx.from magnetometer #2 and 180 cm from magnetometer #1 within the portalcreated by the two magnetometers). The test results are shown in FIGS.15-21. In summary, the results of the experiment described above were asfollows (see also Brief Description of FIGS. 15-21, which furtherexplains the figures and results shown therein):

Effect. (1) Pneumatic rifle (with 40 cm ferromagnetic barrel): Visibleeffect in 250 to 2,000 nanoTesla (nT) (at a distance from themagnetometer between 1.2 and 0.6 meters, respectively) from a pneumaticrifle (see FIG. 15) with a clean background, 2-6 nT when the same personcrosses the portal line (at a distance from the magnetometer between 1.2and 0.6 meters, respectively) without ferro-metallic objects (see FIG.16). (2) Pneumatic pistol (with 10 cm ferromagnetic barrel): Visibleeffect at 15 to 120 nT (at a distance from the magnetometer between 1.2and 0.6 meters) from a pneumatic pistol (see FIG. 17) with a cleanbackground, 2-6 nT (see FIG. 16) (3) The visible effect at 15 to 120 nT(at a distance from the magnetometer between 1.2 and 0.6 meters) of alaptop in a backpack (see FIG. 18) is comparable in modulus with theeffect of the pneumatic gun (with 10 cm long barrel), but it hasdifferent responses from the pistol along the three axes of themagnetometer. Total magnetic strength effect (presented on FIG. 15-21)means modulus of vector calculated from three axis' of magnetometervalues in X, Y and Z directions. (4) The effect 2-30 nT of a safeferro-iron (e.g., phone, keys, coins, etc.) is slightly above thebackground level (see FIG. 19). (5) Noise effect (magnetometers weremounted into the portal at 1 meter above the floor): High-frequencynoise (100 to 500 nT) from the server computer and the microwave portal(see FIG. 20) can be cut off via frequency filtering (a useful effect isbelow 5-10 Hz) (see FIG. 21).

Localization. When two or more people pass through a transmission portalzone simultaneously, localization of a suspicious person can occur via acomparison of the effect modules from the left and right magnetometersand a synchronous photo from a camera.

Expected performance of system with passive magnetometers. Threatobjects detected by passive magnetometry include automatic weapons,guns, and large knives. The area of detection includes the entire body(e.g., front, back, legs, hands, inner body). The stand-off detectiondistance is 2 meters for automatic weapons, and 1-2 meters for smallerguns. The threat localization distance is 0.5 meters. There is noshielding problem in a crowd (e.g., shadowing, transmitting signalsthrough groups of people to detect a threat behind a benign subject)

Block 4—Facial Recognition

Block 4 (optional) provides face recognition based on comparing the faceimage obtained by cameras 9A and 9B (also used in Block 1) with adatabase of known suspicious people. Any know technique can be used forthe data processing. For example, U.S. Pat. No. 6,301,370 discloses animage processing technique based on model graphs and bunch graphs thatefficiently represent image features as jets. The jets are composed ofwavelet transforms and are processed at nodes or landmark locations onan image corresponding to readily identifiable features.

Simultaneous 3D Video and MW Imaging. Additionally, a 3D video image ofthe target may be recorded at the same time of a MW image. In thispreferred embodiment, the method of the invention thus further comprisesforming a 3D optical image of the outer layer of the interrogated space,synchronizing the 3D optical image with the location of the points A1,B1 and optionally C1 and D1, determining points A1′, B1′ and optionallyC1′ and D1′ on the 3D optical image corresponding to the points A1, B1and optionally C1 and D1, calculating the differences P1′=(A2−A1′),P2′=(B2−B1′) and optionally P3′=(C2−C1′) and P4′=(D2−D1′) and comparingthe values P1 with P1′, P2 with P2′ and optionally P3 with P3′ and P4with P4′. Similarly, in the invention a system as described before ispreferred which further comprises at least two cameras recording opticalimages of the interrogated space and being adapted for forming a 3Doptical image of the interrogated space; and a computer which is adaptedfor synchronizing in time and superimposition and digital space of the3D optical image with the 3D MW image formed by the at least twomicrowave sources and at least one microwave receiver of theinterrogated space, which is reflected from the outer layer. Thereflection signal from the outer layer (points A1 and B1) may be fewtimes weaker compared to the reflected signal from the inner layer(points A2 and B2). Points (A1′, B1′) from the outer layer extractedfrom a 3D optical image of the outer layer of the interrogated space(delivered by stereo cameras) can be used to calculate P1′ and P2′ andcompare with P1 and P2.

Preferably, more than 100 microwave sources are used in the method ofthe present invention. It is also preferable to use microwave sourceswhich have a spectrum comprising multiple frequencies.

Preferably, at least two video cameras 9A and 9B (see FIG. 2) recordimages of the target, and the DSP unit 5 reconstructs a 3D video imageof the object. Optical beams do not penetrate the outer boundary (i.e.,the person's outer garment in the example herein). This 3D video imagingis synchronized in time with the 3D microwave imaging. Overlapping the3D video image over the 3D MW image of the outer border can achieveimproved accuracy of the position of the outer border and improvedcalculation of the additional path, h. In one embodiment, the system isadditionally equipped with an automatic alarm, which triggers a sound ora visual alert if the distance h is above a predetermined thresholdvalue and thus the presence of a hidden object(s) is suspected.

In one embodiment the 3D microwave image is formed by illumination ofthe scene by microwave radiation from one emitter and recording thescene image by at least two microwave detectors. In another embodimentthe illumination is performed by at least two separate microwaveemitters that illuminate the scene from different angles, and therecording is performed by one microwave detector.

In one embodiment the microwave emitter radiation is a coherentmicrowave radiation at N frequencies, which optionally can beequi-frequencies, are not related to the lines of absorption of theirradiated media.

The 3D optical image is formed by illumination of the scene by opticalradiation and recording the scene image by at least two opticaldetectors. Different types of processing may apply. In the preferredembodiment, a digital signal processor (DSP) performs a coherentprocessing, which calculates the 3D image taking into account bothamplitude and phase information of electromagnetic fields reflected fromthe interrogated scene.

Parallel data processing occurring on one or more computer processors.The combinatorial processing of data collected by Blocks 1, 2, and/or 3is unique and advantageous. Such parallel and combined processingprovides simultaneous collection and analysis of various data fromcombined threat detection techniques in real time for check points inpublic places such as airports, subway, etc. By processing such data inparallel, rather that separately, the processing time is greatlyreduced, allowing for higher traffic flow without losing efficiency orquality of the threat detection, and in some embodiments, furtherimproving the same while also allowing for higher traffic flow throughthe system.

Wide Angle of Inspection. The present invention is capable of achievinga wide angle of inspection, i.e. greater than 90 degrees perspective ofan inspected area. This wide angle is achieved by an antenna design(emitters, Tx, and receivers, Rx) having a wide directionality range(more than 90 degrees). Tx and Rx antennas are designed as directionalantennas with a wide antenna pattern with a main lobe more than 90degrees at 3 dB beamwidth. See FIGS. 9-11.

Wide Zone of Inspection. The present invention achieves a wide zone ofinspection. The wide zone of inspection is achieved by the followingfeatures: (1) a wide distance between pillars comprising microwaveemitters/receivers (e.g., 2.4 meters between pillars); (2) each pillaris capable of operating as a single system (i.e., transmitters andreceivers in one pillar) and also in combination as a complex system ofpillars (i.e., at least two pillars, each with transmitters and/orreceivers which may correspond with one another); and (3) inspection oftargets from varying angles due to the geometry/setup of the pillars andcameras. See FIG. 12. FIGS. 9 and 10 further show Tx and Rx antennaswhich each individually have a greater than 90-degree lobe. FIG. 11 thenshows an exemplary wide angle of inspection in a chosen geometry ofpillars and FIG. 12 shows a wide zone of inspection, defined by Tx andRx antennas having wide angles, a wide distance between pillars (e.g.,2.4 meters), and a capability of Tx and Rx antennas being located on thesame pillar(s) (i.e., a simple, or independent, system) or a capabilityof Tx antennas being located on one pillar (e.g., left) and Rx antennasbeing located on another pillar (e.g., right), or vise-versa (i.e., acomplex system). Such a setup allows for an inspection of targets fromvarying angles at the same time.

Digital Focusing. The present invention is capable of achieving adigital focusing, rather than a mechanical scanning of the target areaand subject(s). The digital focusing is achieved via coherent processingof the signals received (i.e., including both phase andmagnitude/amplitude data simultaneously). In the prior art, such digitalfocusing is impossible or at least limited by computing resources formoving targets in wide inspection zones. For example, current prior artsystem data scans take a period of tens of milliseconds, but the dataprocessing and analysis of the same scan takes a period of at least afew seconds. The present invention, however, is capable of performingboth the scanning and the processing in real time (i.e., total scanningand processing occurs preferably in less than 50 milliseconds, or 50-60milliseconds, depending of numbers of targets simultaneouslyinvestigated in the inspection zone. Scanning and processing occurs inparallel processors (i.e., the scanning and processing occurssimultaneously).

The digital focusing and real time processing discussed above allow fora high throughput without impeding the flow of targets through theinspection area, a feature which is required in mass transit hubs. Thereal-time operation is a result of, and includes without limitation, thefollowing features: (1) fast switching of a frequency inside of aspecially designed wideband frequency generator (a typical time for suchfast switching, alongside a good frequency stability, is in the range ofa few, e.g., 4-6, microseconds) 131; (2) fast switching of individualantennas within an array by specially designed multilayer electronicboards coupled with multiple output fast keys (a typical time for suchfast switching is in the range of tens of nanoseconds, e.g., 50-100nanoseconds). It is further noted that the fast keys are switched basedon an input signal to one of a set of outputs by command (e.g., fouroutputs). Four such keys are designed in a multiplexer (i.e., one inputto one of 16 outputs by command). Each fast key (e.g., single microchip)thus has one input and four outputs. The boards for one antenna arraymay thus be 256 individual transmitters, which contains 64 fast keys todeliver one base signal, in each frequency, to the individualtransmitters in real time; (3) an algorithm designed to process thesignals received as a result of the fast switching described above, thealgorithm being programmed on a microchip located on an electronic boardand controlled by main processor located within the pillars according tothe present invention. See FIG. 13.

Discussing FIG. 13 further: One frame of processing may be broken downas shown in the figure. Moving from the bottom of FIG. 13 upwards, 135represents the order of time necessary to measure a reflected signalfrom one transmitter (Tx) at one frequency (this occurs on the order of10⁻⁷ seconds), for example, 800 nanoseconds; 134 represents the totaltime of all transmitter switching and signal measurements of alltransmitters at one frequency (this occurs on the order of 10⁻⁵ seconds,as several microwave signals are measured); 133 represents the order oftime necessary to measure reflected signals from all transmitters at onefrequency (this occurs on the order of 10⁻⁴ seconds); 132 represents thetotal time for all transmitter switching at all frequencies combined andsignal measurements of all transmitters at all frequencies combined(this occurs on the order of 10⁻² seconds); 131 represents the number offrames per second (e.g., 15 fps) produced via a microwave signalmeasurement in one frame and within time period of about 50-60milliseconds.

Real-time processing of signals received. An important parameter fordetermining the quality and efficiency of multi-threat detection is thetime in which it takes to collect one frame of data. A typical time forcollecting one frame is about tens of milliseconds, which includes alltargets in a wide zone with fast frequency switching (typically morethan hundred frequencies) and with fast switching of individual antennasin the array (typically, more than one thousand individualtransmitters/receivers in up to four antenna arrays). The presentinvention is capable of capturing 15 or more frames per second of alldetected targets within the inspection zone simultaneously (i.e. oneframe is collected in about 50 milliseconds, processing of the sameframe takes also about 50 milliseconds in parallel to the collectiontime; therefore, the two values determine a value of 15 frames persecond, or more if one of the two values is further shortened). To putthis value of 15 frames or more per second into perspective, thefollowing examples are provided:

Example 1. With a speed of 15 frames per second (fps), and a personmoving approximately 10 cm per frame, the system of the presentinvention captures targets without losing processed information beforethe subject moves too far. If the speed decreases by 5 fps, the systemwould lose a tracked target because that target will have shifted 30 cmand may already cross into a neighboring trajectory channel of waves.Thus, a higher fps allows for such real-time processing while alsoproviding the capability of processing several targets at once. Ingeneral, the more frames per second, the greater the performance andprobability of detection, since all frames are used in the analysisindependently and in combination contribute to any final alarm decision.Current prior art in the field of invention is limited to a maximum of15 fps or to non-moving targets, or both. The present invention operatesat greater than 15 fps and applies to both moving and non-moving targetsat the same rate of 15 fps or more.

Standoff detection at longer distances. The present invention is capableof inspecting an area as long and wide as 3 meters (or less), and/or anarea as long as 6 meters (or less). The size of a given embodiment andinspection area may depend on specific factors such as, but not limitedto, visibility zone of video, visibility zone of microwave imaging, andsystem resolution requirements.

Multi-threat detection of explosives and metallic weaponssimultaneously. Multi-threat detection of both explosives and metallicweapons, at the same time, and in real time, is achieved by thefollowing aspects of the present invention: (1) each transmitter usesthe same source of microwave irradiation; (2) various scatteredpolarization is detected by the same receiving antenna but turned 90degrees (i.e., the same design receiving antenna turned 90 degrees aboutits axis of symmetry, such that the antenna receives cross-polarizationsof transmitted signals); (3) a receiving antenna placed at 0 degrees, inrelation to (2), for collecting initial polarization of transmitted andscattered signals (i.e., for receiving co-polarizations); (4) Acalculated ratio of co-polarizations and cross-polarizations (collectedpreferably as described herein, i.e., antennas placed at “0” and “90”degrees) allows for detection of separate explosives threats andmetallic object threats (see, e.g., FIGS. 14A-14B); and (5) a uniquealgorithm for separately reconstructing two 3D microwave images, onewith regard to co-polarizations and the other with regard tocross-polarizations, for the detection and the separation of multiplethreats potentially located on multiple targets simultaneously and inreal time (i.e., signal measurement in parallel with processing ofsignals measured), which occurs via a final determination made by thesystem after combining information from each 3D microwave image, also incombination with any video images obtained.

High probability of detection coupled with a low false alarm rate. Theability of the present invention to process data in real time, and tocollect and analyze all frames during a subject's movement within thezone of inspection, allow for a high probability of detection. Theability of the present system to combine information from two receivingblocks (e.g., explosives and metal detection) increases the performanceof the processing and analysis of signals but also lowers the chances ofa false alarm which would disturb the movement of all subjects withinthe inspection area.

Applications of the present systems and methods. When planning adeployment of an inspection technology, one should consider both how itwould affect the innocent general public and how it would help toprevent an offender from carrying illicit substances or objects, or aterrorist from carrying out an attack.

In the case of cooperative inspection, the inspected person (whether itis a terrorist or not) always knows about the fact of inspection, whilein the case of non-cooperative inspection, this is not necessarily thecase. Knowing about the inspection deters the terrorist, while alsomaking it relatively easier for the terrorist to prepare for and avoidbeing detected. In the case of non-cooperative inspection, the inspectedtarget may or may not know about the fact of inspection.

In both cases: (1) There is no negative effect of human factor ondetection; (2) Inspection causes no inconvenience for the site; (3)Inconvenience only for those causing false alarms; others are notaffected; (4) No queues, no staff, so the effect of explosion at thecheckpoint could be less deadly.

If the inspection is covert, then there is no risk from explosion at theinspection point, since it is not an attractive target. Also, theprobability of detecting a threat may be higher than if the terrorist isaware of the inspection, even though the nominal detection probabilityof a non-cooperative technology may be lower than that of the technologythat requires cooperation.

With these points in mind, one can envisage two main ways of using thepresent invention: (1) Open inspection, comprising an early warningsystem operating well before the subjects are actually entering theprotected area (e.g., in the street, hundreds of meters away from theentrance to a mass transit hub, such as a stadium or a train station).It will signal the possibility of a high-risk target, which should beattended to by a relevant procedure; (2) Covert inspection: a standalonesystem installed at some distance from the protected area (e.g.,military checkpoint) or within an area, e.g., with high crime risk(e.g., an area with a high proliferation of illegal guns). The systemwill quietly inform the military personnel or law enforcers about thepotential threat or illegal activity. In both cases, the presentinvention can be combined with a facial recognition technology anddatabase, which may provide identification of the threat carrier whilehe or she is still at a safe distance.

Alarm signals produced by the present invention include informationabout the type of the threat and the location of the threat, as well asphotographs of the suspected offenders, which may be used in the contextof a broader security network featuring, e.g., facial recognition,automatic doors, etc.

The present invention generally describes apparatuses, including portalsand detectors for detecting hazardous and/or radioactive materials, andmethods for signal processing, decision making and/or for using theapparatuses. It should be understood that these apparatuses and methodsare adapted to be used on a variety of subjects and in a variety ofsettings, including people, packages, conveyances, buildings, outdoorsettings, and/or indoor settings. Also, within the scope of theinvention is firmware, hardware, software and computer readable-mediaincluding software which is used for carrying out and/or guiding themethodologies described herein, particularly with respect to radioactive(and nuclear) threat detection. Hardware optionally includes a computer,the computer optionally comprising a processor, memory, storage spaceand software loaded thereon. The present invention has been describedusing detailed descriptions of embodiments thereof that are provided byway of example and are not intended to limit the scope of the invention.The described embodiments comprise different features, not all of whichare required in all embodiments of the invention. Some embodiments ofthe present invention utilize only some of the features or possiblecombinations of the features. Variations of embodiments of the presentinvention that are described and embodiments of the present inventioncomprising different combinations of features noted in the describedembodiments will occur to persons of the art. When used in the followingclaims, the terms “comprises”, “includes”, “have” and their conjugatesmean “including but not limited to”. The scope of the invention islimited only by the following claims.

The description of a preferred embodiment of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Obviously, many modifications and variations will be apparentto practitioners skilled in this art. It is intended that the scope ofthe invention be defined by the following claims and their equivalents.

Moreover, the words “example” or “exemplary” are used herein to meanserving as an example, instance, or illustration. Any aspect or designdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe words “example” or “exemplary” is intended to present concepts in aconcrete fashion. As used in this application, the term “or” is intendedto mean an inclusive “or” rather than an exclusive “or”. That is, unlessspecified otherwise, or clear from context, “X employs A or B” isintended to mean any of the natural inclusive permutations. That is, ifX employs A; X employs B; or X employs both A and B, then “X employs Aor B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform.

What is claimed is:
 1. A method for detecting one or more threats on oneor more targets passing through a security area, comprising: calculatinga dielectric permittivity value of one or more objects on said one ormore targets via one or more microwave signals, said dielectricpermittivity value corresponding to a variation in a microwave reflectedor transmitted through said one or more objects, determining a magneticstrength effect value of said one or more objects on said one or moretargets via one or more magnetometers, entering said calculateddielectric permittivity value and said magnetic strength effect valueinto at least one machine learning algorithm, and creating an alarmafter one screening stage if said one or more algorithms indicate athreshold value, said threshold value indicating a threat.
 2. The methodof claim 1, further comprising the step of: processing co-polarizationversus cross-polarization values of said one or more microwave signals,thus forming a polarization ratio value for said one or more objects,and entering said polarization ratio value into said one or more machinelearning algorithms along with said dielectric permittivity value andsaid magnetic strength effect value.
 3. The method of claim 2, whereinsaid dielectric permittivity value and said polarization ratio value arecollected at a speed of at least 15 frames per second (fps).
 4. Themethod of claim 1, further comprising Principal Component Analysis (PCA)pre-processing.
 5. The method of claim 1, comprising at least twoalgorithms, wherein either algorithm may indicate a threat without aneed for both algorithms to indicate said threat.
 6. The method of claim1, wherein at least one algorithm is a Mahalanobis distance algorithm.7. The method of claim 1, wherein at least one algorithm is a supportvector machine (SVM) algorithm.
 8. The method of claim 1, furthercomprising performing a noise cutoff using frequency filtering.
 9. Themethod of claim 1, wherein at least two magnetometers are employed todetermine said magnetic strength effect value.
 10. The method of claim9, wherein results from a first magnetometer are compared with resultsfrom a second magnetometer.
 11. The method of claim 9, wherein the atleast two magnetometers form a portal up to 2.5 meters wide.
 12. Themethod of claim 10, further comprising a camera, said camera taking aphoto, said photo being synchronous with said compared results betweensaid magnetometers.
 13. The method of claim 1, further comprisingperforming a facial recognition of a target, wherein said facialrecognition is performed via one or more video cameras.
 14. The methodof claim 1, wherein at least 2 video cameras are employed to construct a3D video image of the one or more objects, said 3D video image beingcomplementary to a 3D microwave image of said objects, said at least 2video cameras being synchronized in time with said one or more microwavesignals.
 15. The method of claim 1, wherein the alarm differentiatesamong a target without objects, a target with a metal, and a target witha dielectric.
 16. The method of claim 1, wherein the alarmdifferentiates among benign metal objects and threatening metal objects.17. The method of claim 1, further comprising displaying results via agraph, said graph differentiating an algorithmic output value via coloror shape or both color and shape.
 18. The method of claim 1, wherein thealarm is a silent alarm.
 19. The method of claim 1, said method beingcapable of detecting metallic objects being shadowed by one or moreother targets within the area.
 20. The method of claim 1, said methodbeing capable of detecting metallic objects inside said target's body.21. A method for detecting one or more threats on one or more targetspassing through a security area, comprising: calculating a dielectricpermittivity value of one or more objects on said one or more targetsvia one or more microwave signals, said dielectric permittivity valuebeing collected at a speed of at least 15 frames per second, determininga magnetic strength effect value of said one or more objects on said oneor more targets via one or more magnetometers, entering said calculateddielectric permittivity value and said magnetic strength effect valueinto at least one machine learning algorithm, and creating an alarm ifsaid one or more algorithms indicate a threshold value, said thresholdvalue indicating a threat.